This invention relates to a system for improving the display of medical images of internal organs and tissue such as produced by x-ray, CAT scan, or MRI.
Medical images of internal organs and tissue are typically viewed one frame at a time. This process is time consuming and it may result in significant diagnostic indicia being overlooked wherein the diagnostic indicia is represented by changes or differences between related medical images such as images taken at successive time intervals or images which are taken from spatially separated slices through internal organs or tissue. Accordingly, there is a need to display medical images in a manner to make such changes or differences more noticeable. One way to make changes more noticeable is to display successive images as a motion picture. In the case of successive images displaced in time, the images would appear as a motion picture provided the successive images are taken at short enough intervals to avoid excessive changes from image to image. In a practical system, the display of such successive images does not result in a motion depiction in which the depicted objects transform smoothly, because the changes between the successive images are too great and abrupt changes typically occur from image to image resulting in the depiction being xe2x80x9cjerkyxe2x80x9d and difficult to follow. The above problem, of course, could be solved by simply taking the images closer together in time. But this solution is impractical, if not impossible, because of the number of images required and the time required to obtain each image.
In accordance with invention, a series of related medical images are generated by x-ray, CAT scan, or MRI. The images may be taken at regular or irregular time intervals or they may be taken from regular or irregular spaced slices through an organ or tissue.
In the case of successive images corresponding to incrementally spaced slices through an organ or tissue, the successive images can be shown as a motion picture. In such a display, the depicted organs or tissue will appear to transform their shape and characteristics as the successive images are displayed. If the slices are close enough together, the resulting display will appear as a quality motion picture, in which the depicted organs or tissue transform smoothly as the successive images are displayed.
In the preferred embodiment, the images are spaced temporally or spatially in accordance with what is practical, resulting in substantial changes between successive images, so that a display of the successive images as a motion picture would not provide a smooth depiction of the transformation of the depicted image objects. The medical images, if not already represented as pixels in digital form, are converted to such form. The resulting image data is then analyzed to generate dense motion vector fields representing the apparent motion of image elements from the frame to frame in the sequence of related medical image frames. When the successive images are at successive intervals of time the image elements represent small pixel sized pieces of depicted objects. If an object is moving or changing as represented in adjacent frames, then the image elements of such objects will move with the object. If a depicted the object is stationary then the dense motion field vectors will be zero for the image element making up the stationary object. A dense motion field comprising a vector for each pixel, will be generated for each pair of adjacent frames.
When the sequence of medical images represents spaced slices through an organ or tissue, the same image elements will usually not be found in successive frames, since each frame will represent a different slice. The dense motion vector field analysis will never-the-less locate corresponding image elements in successive frames as if the successive frames represented motion from frame to frame, and the vectors of the dense motion vector field will represent any displacement between the corresponding image elements in successive frames.
In accordance with the invention, the dense motion vector fields are used to generate interpolated frames between the original sequence of frames. The interpolated frames are interlaced with the original sequence of frames so that when the sequence of frames with the interpolated frames are displayed in sequence at a motion picture rate, i.e. at least 15 frames per second, the change between successive frames will be depicted as smooth motion or transformation from frame to frame.